php - mysql 如何合并具有相同 id 的多行

Question

我是新来的，但到目前为止，社区是我项目中最好的资源。 我是一个“想成为”的愚蠢/虚拟的 Mysql，而我正处于一个让我发疯的项目之中。

我有一个来自 wordpress 插件 buddypress 的表，它将 meta_key 和 meta_values 配对，以便创建类似于分类法的东西。我的职责是使用这些配对值来实现高级组搜索。这是原始表格:

--------------------------------------------
id | group_id | meta_key           | meta_value
--------------------------------------------
1  | 1        | time-zone          | Kwajalein
2  | 1        | playstyle          | hardcore
3  | 1        | recruiting-status  | Open
4  | 1        | ilvl               | 115
5  | 1        | main-raid          | Final Coil of Bahamut
6  | 1        | voicechat          | fc.teamspeak3.com

等等......

使用 View ，我设法为初学者创建了一个更友好的可搜索表:

---

gid| time-zone| playstyle  | main-raid
--------------------------------------------
1  |          |            | 
1  |Kwajalein |            | 
1  |          | hardcore   | 
1  |          |            | 
1  |          |            | Final Coil of Bahamut
1  |          |            | 

这是查看代码:

SELECT distinct
group_id AS 'gid',
IF(meta_key='recruiting-status',meta_value,'') AS 'Recruitment',
IF(meta_key='server',meta_value,'') AS 'server',
IF(meta_key='time-zone',meta_value,'') AS 'tzone',
IF(meta_key='main-raid',meta_value,'') AS 'raid',
IF(meta_key='raid-days',meta_value,'') AS 'days',
IF(meta_key='playstyle',meta_value,'') AS 'playstyle',
IF(meta_key='raid-progression',meta_value,'') AS 'progression',
IF(meta_key='raid-time',meta_value,'') AS 'time',
IF(meta_key='tanker-spot',meta_value,'') AS 'tank',
IF(meta_key='healer-spot',meta_value,'') AS 'healer',
IF(meta_key='melee-dps-spot',meta_value,'') AS 'melee',
IF(meta_key='ranged-dps-spot',meta_value,'') AS 'ranged',
IF(meta_key='magic-dps-spot',meta_value,'') AS 'magic',
IF(meta_key='ilvl',meta_value,'') AS 'ilvl',
IF(meta_key='voicechat',meta_value,'') AS 'voice',
IF(meta_key='voicechatpass',meta_value,'') AS 'voicep',
FROM wpstatic_bp_groups_groupmeta

重点是，我需要合并该结果( View )，以便所有 group_id=1 或 2 或 3 等位于一行中，如下所示:

---

gid| time-zone| playstyle  | main-raid
--------------------------------------------
1  |Kwajalein | hardcore   | Final Coil of Bahamut
2  |SaoPaulo  | regular    | Second Coil of Bahamut

等等

有人可以帮我吗？

Answer 1

只需将 IF 放在 MAX 中，或另一个将捕获非空字符串的聚合函数(例如 GROUP_CONCAT) ，并在末尾添加一个GROUP BY group_id。例如，

SELECT
group_id AS gid,
MAX(IF(meta_key='recruiting-status',meta_value,'')) AS 'Recruitment',
MAX(IF(meta_key='server',meta_value,'')) AS 'server',
...
FROM wpstatic_bp_groups_groupmeta
GROUP BY group_id